The Division of Neurobiology and Behavior consists of five independent sections: mammalian neurophysiology, invertebrate neurobiology, neuropsycholgy, neurochemistry and neuromorphology. The overall goal of the research of this Division is to provide a cellular analysis of behavior in selected vertebrates and in Aplysia. Because brains of higher mammals contain trillions of nerve cells and the simplest behaviors involve actions of diverse cells with extremely complex interconnections, it is our approach to reduce experimental material to manageable proportions. In higher animals, complexity can be simplified by selecting particular brain areas for study. Thus, many important types of discriminative behavior depend critically upon neural transformations that occur in the first few relays involved in the processing of sensory information by the nervous system. In Aplysia, a small number of identified neurons can mediate complex behaviors. Because these cells can be studied individually by electrophysiological, biochemical and morphological techniques, it is possible to correlate behavior and learning with neural function.